How Quantum Tunnelling Became Macroscopic

For more than a century, physicists have tried to understand whether the strange behaviour of the quantum world could ever be observed beyond atoms and subatomic particles. Early theories, such as George Gamow’s explanation of tunnelling in nuclear decay, revealed that tiny particles can sometimes pass through barriers instead of bouncing back. This idea challenged common sense and inspired a long scientific quest. Many researchers wondered if quantum behaviour could ever be seen in larger systems, where countless particles act together. The dream was to test quantum mechanics on a scale closer to everyday experience.

That goal was finally achieved through the work of Clarke, Devoret and Martinis, who showed that macroscopic quantum tunnelling and energy quantisation can take place in a superconducting electrical circuit. In their experiments, billions of electrons moved collectively as a single quantum system, which allowed the circuit to tunnel from one state to another and absorb energy in quantised steps. Their results demonstrated that theoretical predictions from decades earlier were correct. The experiments also underscored the conceptual continuity between microscopic quantum theory and visible, measurable systems that can be held in the hand.

These achievements have opened the door to new technologies and deeper scientific questions. Josephson junctions, once used mainly for precision measurements, are now central to quantum circuits and superconducting qubits. They help bridge the gap between fundamental physics and practical applications such as quantum computing. By tracing this history, we can see that scientific progress is cumulative, as each generation builds on earlier discoveries. The work of the 2025 laureates shows that the quantum world is not confined to the invisible realm of particles. It can shape the future of technology on a scale we can see, measure and design.